VoL. 11, 1925 PALEONTOLOGY: P. SUSHKIN 299, These more or less compressed and highly lignified fossil seeds are larger than those of any of the existing Malayasian species known to me, but may be matched by the seeds of several existing African species, among which they most resemble those of the so-called Abyssinian banana, Musa ensete Gmelin. Banana-like leaves, described by paleobotanists under the name of- Musaphyllum, have long been known from the Eocene of the western United States and from the later Tertiary of Central and South America, and Europe, but it is altogether impossible to distinguish the leaves of Musa from those of the related American genus Heliconia. In the case of the seeds, however, this uncertainty disappears, for the seeds of Musa are perfectly characteristic and strikingly different from those of all the other genera of the family Musaceae. The present discovery shows' that Musa was an undoubted member of American Tertiary floras, and although it does not necessarily prove that. the banana was'brought into cultivation by the aborigines in the Western Hemisphere, it lends probability to such a belief, and in a measure serves. to substantiate the statement of the Peruvian author Garcillaso de la Vega. (1530-1568) that the banana was one of the staples of the aborigines before. the discovery of America, or that of Montesinos (1527), as quoted by the- historian Prescott, that the natives of Tumbez brought bananas as an offering to Pizarro when he disembarked.

OUTLINES OF THE HISTORY OF THE RECENT FA UNA OF PALAEARCTIC ASIA By PsTUR SUSHKN RussIAN ACADEMY OF SCIENCES, PECTROGRAD Read before the Academy April 27, 1925 I wish to thank the Local Committee of the. Academy for the oppor- tunity of presenting'to you my Vriews concerning the history of, the recent. fauna of Slberia and High Asia. These views are the, result of studies based in part.on my field work in the Kirghiz Steppe, in southern Siberia and in N. W. Mongolia. At present; Inost zogeographers adopt the.divisions of Palaearctic Asia. into~two subregions: the:Northern, which extends across the Eurasian: continent f-rom' the Pacific to -the Atlantic; .and the more southern, or High Asian.:. For the Northern subregion, most.of the Russian zobgeog- raphers adbpt a further subdivision, proposed .by N. Severtzoff,. into tSree provinces: one;~the -Tundra or northern barren grounds;-twoj, the TaXga- or coniferous' Woodland; and, three, the-Steppe and ForeEt.Steppe-simpk Downloaded by guest on September 28, 2021 300 PALEONTOLOGY: P. SUSHKIN PROC. N. A. S. prairie or prairie with scattered forests. These divisions run across the continent along the parallels of latitude, but the Steppe province is largely interrupted in southern Siberia. Of the divisions of the High Asian sub- region, I shall mention here only the Mongolo-Tibetan province, which embraces practically the whole elevated desert region of Central Asia. These divisions are based on the recent distribution of the fauna with- out any relation to its history, and the principal divisions are considered those which are characterized simply by a large number of species. They have been elaborated primarily for birds, but hold good for other groups also. Historical *and causal understanding of these relations may be arrived at by grouping together the species having the same distribution, and by taking into consideration their ecology, the amount of their structural differences, and the facts of palaeogeography. Starting with the study of birds, I have found that nearly one half of the fauna of every locality in Palaearctic Asia consists of species which may be termed transpalaearctic, since they extend from ocean to ocean: some of them are also widely dis- tributed from north to south, whereas others are restricted to one of the zonal provinces. Such distributions are of recent date, being in harmony with the landscape and other conditions of the present time. The remain- der consists of groups of more restricted distribution. For Siberia, leaving out the transpalaearctic elements, the important groups are: on the east, the Transyenissean, or East-Siberian, group with its subdivisions, and on the west, the West-Palaearctic and West-Siberian groups. The demar- cation line between them runs, roughly speaking, along the Yenissei River and then sweeps westward round the Altai highland. I have found that the Transyenissean species are strongly characterized, some presenting characters of relatively high antiquity; moreover, this group is intimately connected with the fauna of High Asia, many species reaching southward as far as the southern limits of the palaearctic; some of the Transyenissean forms are surely of southern origin. On the other hand, the fauna of westerm Siberia is in the main common with that of Europe; its distinctive forms are not numerous and are feebly characterized. I found this true for birds and butterflies; by others, the same features of East Siberian and West Siberian faunae have been pointed out for dragonflies, Trichoptera, and mammals. These facts find no explanation in recent conditions, but they are in full harmony with the palaeogeography of these regions. The transyenissean elements, strongly characterized, with features of antiquity and presenting relations to the fauna of High Asia-in spite of present differences of physical geography-correspond to the territory of that part of the Eura- sian dry land which is known as the Angara continent. Westerm Siberia is a new dry land which emerged only at the beginning of the second half Downloaded by guest on September 28, 2021 VOL. 11, 1925 PALEONTOLOGY: P. SUSHKIN 301 of the Tertiary, and underwent considerable restriction of its area in later times. With this corresponds the paucity and prevailingly youthful character of its endemic forms. The transpalaearctic distributions which prevail now are features of a later time, and for some of the animals in- volved traces of their Angaran, or western, origin may be found. Details of present distribution, together with facts of geology, soil science, botany and palaeontology show the following course in the later history of the country. The pliocene climate was humid and mild; fall of temperature resulted in local glaciations and has conditioned an exchange of the faunas between the arctic zone and South-Siberian mountains. The glacial period was followed by a dry period, when the conditions of a dry climate and the elements of the steppe reached northward even beyond 600 n. lat., and at that time the saiga antelope roamed as far north as the Vilui River; about the same time, a northward migration of the alpine elements of High Asia took place and the wild sheep of Altai extended nearly 400 miles further north than now., After that came a spreading of the woodland, which has now invaded the alpine zone and the steppe land- scape, and has broken up the province of the steppe. The climate did not, however, return to the favorable type of the preglacial time, being generally cold and dry. Owing to these factors, many gaps in distribution peculiar to Siberia have been caused. This type of climate, with normally hot summer but exceedingly cold, though snowless, winter, is due to the pe- culiarities of the distribution of atmospheric pressures. And this, in turn, is conditioned by the proximity of the extensive elevated plateaus of High Asia. Their upheaval .became fatal for the climate of Siberia. The fauna of High Asia is also strongly characterized, harmonizing well with the old age of this dry land. Prevalent in the fauna are biological types characteristic of desert, of mountain, and especially of dry highland, Sharp characteristics, and in some.cases geographical distribution, of these biological types tell of a long duration of recent conditions. But at the same time, the distribution of the fauna presents many gaps and many isolated remnants, these isolated colonies often having failed, as yet, to develop local characters. And all species which present an interrupted distribution are types characteristic of a more fertile landscape. These facts tell clearly of the extensive devastations to which the fauna has been recently subjected. My interpretation is, that present ecological types, and corresponding environment, are of an old origin. But that their present dominance is a new fact. I deny completely the theory of a large inland basin within the territory of High Asia in the Tertiary, and I consider the country as having presented the conditions of a continental climate, the land being more fertile, though with patches of desert here and there, and the rainfall more abundant than now. Downloaded by guest on September 28, 2021 302 PALEONTOLOGY: P. SUSHKIN PROC. N. A. S. Distribution of the true pheasants permits the location of one of these primary isolated foci of the desert, namely- in the western Gobi, east of the lake Lobnor. Extension of the desert began in Pliocene (though the eastern Gobi has not yet been invaded), whereas N. W. Mongolia and Dzungaria have been conquered by the desert only much later-N. W. Mongolia about the close of glacial time. In its recent fauna, local desert types are just beginning to develop, strongly characterized desert types are all immigrants, 'and well characterized local forms are not desert types. Thus, speaking briefly, we have for Siberia. elements of old Angaran fauna overlaid by modernized transpalaearctic' distributions, the last in- fluenced, in turn, by the glaciation, by the transient spreading of the faunas of the Steppe and High Asia, and by the general deterioration of the cli- mate, which never returned to its preglacial type. For central Asia, we have encroachment of desert and also upheavals which resulted in a. spreading of.the types now prevailing, and in the suppression of others. The Mongolo-Tibetan province, in its present zoological character and limits is a new phenomenon, based on hypertrophy of some of its ancient elements. Concerning 'the southeast corner of .palaearctic Asia, I agree with N. Severtzoff that it presents a remnant of the old palaearctic fauna. At present, being isolated by enormous upheavals, it exists under conditions Which favor the invasion into it of the Indo-Malayan fauna. Many of the palaearctic forms and-some even of the more northern species seem to have originated here. I have no time to consider in detail the complicated faunal relations between Siberia and North America. It is, however, to be noted that the interchange was very prolonged, some of the forms common to both continents (or represented.by related types) having originated in Asia, others in America, and some almost certainly within the territory of the- former land connection itself-a land which may be called Beltringia. One of the most interesting and best established examples is that of the wild sheep. M. Severtzoff and Prof. Nassonov, after studying the distribution and structure of- the wild sheep, have both come to the concl.usion, that this genus migrated-from High Asia to America, before the last glaciation; that in America. they were driven south by the glaciation; that afterwards the American stock spread again to the north and gave origin to another group; and finally that this new group spread back into the Asian continent and occupied eastern Siberia1, so that the.present Siberian sheep stand, geographically and structurally, in no-close relation with th .sheep of High Asia. It may. be mentioned. that a similar course of .migration, is npw- ad- mitted for certain human tibes. - .. Downloaded by guest on September 28, 2021